There are alternatives to BS 5266 Part 1, I would suggest reference to ISO 16069 Safety wayguidance systems is worthy of consideration for designers. I obviously have a vested interest in photoluminescent safety wayguidance system as they pay my salary however these systems now have considerable provenance for risk appropriate based applications. Low proximity escape illumination systems can offer the risk assessor, competent and responsible person another dimension for consideration remembering the first place that smoke goes is the ceiling to obscure traditional lighting without any mains power failure occurance. These systems are now compulsory within stairways, in all tall buildings in New York. This is a direct function of the value of the systems experienced by successful evacuees in the horrors of 9/11.